Drought survival strategies of juvenile bromeliads of Alcantarea imperialis (Carriere) Harms

The establishment of bromeliad populations in rupicolous environments depends on the efficient survival strategy of juvenile individuals under adverse conditions, such as drought. Juvenile plants of Alcantarea imperialis do not form water reservoir (phytotelm) as adult individuals and then they require metabolic mechanisms to cope with water deficit during the initial stages of plant growth. It has been reported that sugar accumulation and crassulacean acid metabolism (CAM) photosynthesis are related to plant responses to water deficit. This study investigated whether these physiological adjustments could be dual strategies to drought survive of juvenile A. imperialis plants. Plants were cultivated in vitro with polyethylene glycol 6000 (PEG 6000) to simulate different degrees of water deficit (moderate stress, - 1.9 mega Pascal (MPa) and severe stress, - 8.5 MPa) and a control treatment without PEG (- 0.5 MPa) for 7, 15 and 30 days. Plant growth, biochemical and anatomical parameters were analyzed. Under 15 days in moderate stress condition, the plants initially accumulated soluble sugars and at 30 days, their leaves presented a thicker aquiferous parenchyma, which might facilitate the accumulation of high concentrations of carbohydrates and polyalcohols (sorbitol and mannitol) and perform CAM pathway due to the increase of phosphoenolpyruvate carboxylase (PEPC) activity and accumulate organic acids during the night. Under severe stress CAM was intensified and their leaves were less thick. The results showed that juvenile A. imperialis plants are able to make metabolic adjustments in response to water shortage, and these responses are dependent on the intensity and/or duration of the drought conditions. Overall, this work provides a better understanding of how rupicolous plants survive under different drought conditions. Key message Rupicolous juvenile bromeliads of Alcantarea imperialis subjected to drought are able to survive by increasing the production of sugars under conditions of moderate stress or performing CAM under severe stress.